Alpha, OH, United States
Alpha, OH, United States

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Brownson D.A.C.,Manchester Metropolitan University | Figueiredo-Filho L.C.S.,Federal University of São Carlos | Figueiredo-Filho L.C.S.,Federal University of Paraná | Riehl B.L.,SCNTE LTD. | And 5 more authors.
Journal of Materials Chemistry A | Year: 2016

The fabrication of a freestanding three-dimensional (3D) graphene nano-ribbon open cell foam electrode is reported based upon a facile high temperature (1700°C) low vacuum (50 Torr) process. The graphene nano-ribbon (GNR) foam comprises on average 4 graphene layers and has an O/C ratio of 0.14; a quasi-graphene structure. This unique material is demonstrated to be electrochemically useful, with the electrochemical properties and resultant electroanalytical performance of the novel freestanding 3D GNR foam electrode reported for the first time. Electrochemical characterisation is performed via cyclic voltammetry in aqueous solutions using a range of electro-active redox probes and biologically relevant analytes, namely potassium ferrocyanide(II), hexaammineruthenium(iii) chloride, uric acid (UA), acetaminophen (AP) and dopamine hydrochloride (DA). Analytical performance is evaluated and benchmarked through comparisons of the 3D GNR foam to other carbon based 3D foam electrodes, namely pristine graphene and reticulated vitreous carbon (RVC) alternatives. We show that the 3D GNR foam electrode possesses favourable heterogeneous electron transfer (HET) properties when compared to the alternative carbon based 3D foams, likely due to improved coverage of reactive edge plane like-sites/defects on its structure. In terms of the electroanalytical response of the 3D GNR foam electrode, it is found to give rise to an improved linear range and limit of detection towards some analytes; however, in certain cases the alternative carbon based 3D foams out-performed the GNR foam. These findings question the need of 'only' fast HET properties and suggest a compromise is required (for improved sensing capabilities to be realised) between HET speeds, the presence/absence of oxygenated species and the accessibility of the electrode's active surface area. This work offers insight to those working in the field of electrochemistry, particularly electroanalysis and those searching for new carbon based 3D foam electrode materials. © The Royal Society of Chemistry 2016.

Yue W.,University of Cincinnati | Bange A.,Xavier University | Riehl B.L.,SCNTE Ltd. | Riehl B.D.,SCNTE Ltd. | And 3 more authors.
Electroanalysis | Year: 2012

Anodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV) were used to determine Mn concentration using metal catalyst free carbon nanotube (MCFCNT) electrodes and square wave stripping voltammetry (SWSV). The MCFCNTs are synthesized using a Carbo Thermal Carbide Conversion method which results in a material that does not contain residual transition metals. Detection limits of 120nM and 93nM were achieved for ASV and CSV, respectively, with a deposition time of 60s. CSV was found to be better than ASV in Mn detection in many aspects, such as limit of detection and sensitivity. The CSV method was used in pond water matrix addition measurements. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang T.,University of Cincinnati | Schlueter K.T.,Yellow Springs Instruments Inc. | Riehl B.L.,SCNTE LLC | Johnson J.M.,Yellow Springs Instruments Inc. | Heineman W.R.,University of Cincinnati
Analytical Chemistry | Year: 2013

A novel method for the detection of nitrate was developed using simplified nitrate reductase (SNaR) that was produced by genetic recombination techniques. The SNaR consists of the fragments of the Mo-molybdopterin (MO-MPT) binding site and nitrate reduction active site and has high activity for nitrate reduction. The method is based on a unique combination of the enzyme-catalyzed reduction of nitrate to nitrite by thin-layer coulometry followed by spectroscopic measurement of the colored product generated from the reaction of nitrite with Griess reagents. Coulometric reduction of nitrate to nitrite used methyl viologen (MV2+) as the electron transfer mediator for SNaR and controlled potential coulometry in an indium tin oxide (ITO) thin-layer electrochemical cell. Absorbance at 540 nm was proportional to the concentration of nitrate in the sample with a linear range of 1-160 μM and a sensitivity of 8000 AU M-1. The method required less than 60 μL of sample. Detection of nitrate could also be performed by measuring the charge associated with coulometry. However, the spectroscopic procedure gave superior performance because of interference from the large background charge associated with coulometry. Results for the determination of nitrate concentration in several natural water samples using this device with spectroscopic detection are in good agreement with analysis done with a standard method. © 2013 American Chemical Society.

Yue W.,University of Cincinnati | Riehl B.L.,SCNTE LTD | Pantelic N.,YSI Incorporated | Schlueter K.T.,YSI Incorporated | And 5 more authors.
Electroanalysis | Year: 2012

Anodic stripping voltammetry (ASV) determination of Pb 2+, Cd 2+, and Zn 2+ was done using metal catalyst free carbon nanotube (MCFCN) electrodes. Osteryoung square wave stripping voltammetry (OSWSV) was selected for detection. The MCFCNTs are synthesized via Carbo Thermal Carbide Conversion method which leads to residual transition metal free in the CNT structure. The new material shows very good results in detecting heavy metal ions, such as Pb 2+, Cd 2+, and Zn 2+. The calculated limits of detection were 13nM, 32nM and 50nM for Pb 2+, Cd 2+ and Zn 2+, respectively with a deposition time of 150s. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A process for producing a nanostructured carbon material including the steps of providing a metal or metalloid carbide substrate and reacting the carbide substrate with a reactive gas to form the nanostructured carbon material, the reactive gas and the carbide substrate being added during the reacting step.

Wang T.,University of Cincinnati | Manamperi H.D.,University of Cincinnati | Yue W.,University of Cincinnati | Riehl B.L.,SCNTE LLC | And 3 more authors.
Electroanalysis | Year: 2013

A novel catalyst free carbon nanotube (CNT) electrode was fabricated by a Carbo Thermo Carbide Conversion (CTCC) method. The morphology and nanostructure of the CNT electrodes were characterized by transmission electron microscopy (TEM) and Raman spectroscopy. Electrochemical characterization using potassium ferricyanide, ferroin and catechol shows these CNTs have higher current capacity, faster electron transfer rate and larger microscopic surface area than glassy carbon (GC) electrode. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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